Rotary shafts – gudgeons – housings – and flexible couplings for ro – Separate coupling device movable radially of axes of torque...
Reexamination Certificate
2001-12-14
2002-10-15
Browne, Lynne H. (Department: 3679)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Separate coupling device movable radially of axes of torque...
C464S903000, C464S153000
Reexamination Certificate
active
06464589
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to flexible couplings for rotary shafts, more particularly to rotary shaft couplings which accommodate misaligned drive axes with radial movement of a transverse cylindrical torque transmitting engagement member, and most specifically to rotary shaft couplings which accommodate misaligned axes with radial movement of a transverse cylindrical torque transmitting engagement member primarily produced by molding.
2. General Background
Oldham type rotary shaft couplings that use a radially moveable torque transmitting engagement member are well known in the art. Modification of the Oldham principle by using a substantially cylindrical engagement member is also known. By using mating male and female members which respectively present a transverse projection and a recess that engage over half of a cylindrical form the coupling can accommodate large parallel, i.e. offset, misalignment of axes while also providing against the axial disconnection inherent to an Oldham type rotary shaft coupling. Given two pairs of perpendicularly opposed male and female mating substantially cylindrical engagement members with sufficient spacing between the three bodies large angular, in addition to large offset, misalignments are readily accommodated.
The male projection must, however, possess a convex substantially cylindrical exterior surface which is further undercut in connection to the body concerned. This is considered a particularly difficult configuration to either machine or mold. The female cavity can easily be effected with an appropriate transverse drilling of the body concerned but replicating the opposite form by machining requires rotation of the body relative to the cutting tool during cutting repeatedly along the entire length of the cylindrical projection desired as the radius of the cutting tool is restricted by the relatively small radius of the cylinder approximated in comparison with the length required of this form.
The undercut required to present the majority of a cylindrical form, moreover, presents problems to molding the male engagement member. Molding of the female engagement member is considered less problematic if no additional undercut is incorporated. The substantially cylindrical cavity must be effected by a machined substantially cylindrical projection and any additional undercut inhibits release of the molded part from this projection.
DISCUSSION OF THE PRIOR ART
An early example of a rotary shaft coupling using substantially cylindrical male and female engagement members is found in U.S. Pat. No. 1,298,680 for a ‘Flexible Coupling’ issued Apr. 1, 1919 to J. R. Dunham. The female members in this coupling have two perpendicularly disposed substantially cylindrical grooves (
5
) which intersect. One male member or knuckle rib (
4
) is also equipped with a similar cylindrical groove (
4
′) to accommodate the opposed knuckle rib (
9
). The female member is hence essentially a cylindrical body with transverse perpendicular grooves (
5
) open to opposed faces of the body pivotably encasing the two opposed, engaged, knuckle ribs. Each terminal end has a knuckle rib (
4
) with a transverse substantially cylindrical groove (
4
′) encased by a female body member. A medial male unit (
7
) has two opposed knuckle ribs and five components comprise the basic structure of the coupling about which a simple cylindrical shell is disposed to encase the coupling, retain lubrication used thereupon, and limit excessive lateral movement.
A simplification, in the number of components, of this same basic approach is found in U.S. Pat. No. 2,251,126 for a ‘Molded Composition Slipper Bearing’ issued July 29, 1941 to T. L. Gatke that uses only three components: a female coupling end with a transverse substantially cylindrical groove, a male coupling end with a uniform projection having a transverse cylindrical aperture open to either of two parallel faces, and the slipper bearing which fits in the cylindrical groove of the female coupling end and has a reduced diameter transversely disposed cylindrical pivot through the aperture through the male projection. The slipper bearing is pivotably held in a cylindrical transverse groove of the female coupling end by opposed heads that are semicircular in the plane normal the transverse axis of the groove and transversely elongated parallel that groove to fit the same.
Most significantly, however, the slipper bearing, which possesses a rather complex configuration with two partly and one full cylindrical exterior surfaces, is molded of composition material. Woven fabric, which can be reinforced with wire, provides a core which is laminated with a non-metallic material, i.e. resin, impregnated therein bonding the fabric layers together and providing a hard ‘envelope’ suited to a bearing surface. The laminated fabric core provides resilient strength for impact resistance. The heads of the slipper bearing are specifically made in this manner and are apparently of one piece with the reduced diameter pivot shaft between the two heads which is further apparently enclosed by the engaging male member. How this construction is achieved is not explained however.
U.S. Pat. No. 2,260,567 issued Oct. 28, 1941 to the same inventor and possessing the same title, though resulting from a separate and earlier application, addresses this practical difficulty by making the slipper bearing from several different components, two heads and the connecting shaft, held together with a nut and bolt and other hardware including washers, bushings, and two hubs between the heads and the cylindrical shaft compressed therebetween. This construction enables practical use of a male member having a through hole open to either of two opposed, flat, parallel faces as the shaft of the bearing can be disposed in this through hole and the heads attached to either end of the shaft with the nut and bolt. The head of the bolt and the nut are each disposed in an open cavity of one head and practical resolution of this ‘simplification’ is seen to involve over a dozen separate elements assembled together to provide this one component.
U.S. Pat. No. 4,941,861 issued Jul. 17, 1990 to Robert A. Painter for an ‘Interlocking Shaft Coupling’ discloses use of only three molded plastic components engaging each other with two pairs of substantially cylindrical transverse male and female elements. While the medial ‘disk shaped body’ is shown (
FIG. 2
) in an alternative arrangement having two transverse perpendicular substantially cylindrical grooves each open to an opposed face, no mating male elements are shown, and the only full depiction of the coupling utilizes male elements upon the medial component and one mating female element upon each terminal component. It is also noted that the grooves depicted in this alternative medial ‘disk shaped body’ clearly both possess a depth exceeding half the width of this body and must therefore intersect and prevent engagement by the two male elements necessary for torque transmittal.
This intersection is not depicted though a central hole is depicted in one (
FIG. 3
) of the versions of this medial ‘disk shaped body’ with two perpendicular transverse substantially cylindrical male elements which is explained, in the most specific reference found to the molding preferred, as being desirable because “(w)hen plastic is molded, areas with different cross-sectional thicknesses typically cure at different rates” and the overlap of male elements would, absent the ‘central hole’ be “about one and one-half times as thick as any other part” by which it is understood that the thickness of the medial ‘disk shaped body’, as depicted in every instance, is approximately equal in thickness to the height of the male element or the depth of the female element. Secondly, this ‘hole’ serves as a recess for a ‘central protrusion’ upward from the bottom of each transverse substantially cylindrical groove required to prevent lateral displacement and disengagement of the coupling (
FIG
Browne Lynne H.
Gibson Peter
Thompson Kenneth L.
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